The effect of dispersion on long-range inspection using ultrasonic guided waves (1)

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1、NDT&EInternational34(2001)1±9www.elsevier.com/locate/ndteintTheeffectofdispersiononlong-rangeinspectionusingultrasonicguidedwavesP.Wilcox*,M.Lowe,P.CawleyNDTLaboratory,DepartmentofMechanicalEngineering,ImperialCollege,ExhibitionRoad,LondonSW72BX,UKReceived31January2000;receive

2、dinrevisedform31March2000;accepted3April2000AbstractThedispersionofultrasonicguidedwavescauseswave-packetstospreadoutinspaceandtimeastheypropagatethroughastructure.Thislimitstheresolutionthatcanbeobtainedinalong-rangeguidedwaveinspectionsystem.Atechniqueispresentedforquicklypr

3、edictingtherateofspreadingofadispersivewave-packetasitpropagates.Itisshownthatthedurationofawave-packetincreaseslinearlywithpropagationdistance.Itisalsoshownthatthedurationofawave-packetafteragivenpropagationdistancecanbeminimisedbyoptimisingtheinputsignal.Adimensionlessparame

4、tercalledminimumresolvabledistance(MRD)isde®nedthatenablesadirectcomparisontobemadebetweentheresolutionattainableatdifferentoperatingpoints.SomeconclusionsaremadeconcerningtheresolutionofvariousoperatingpointsforthecaseofLambwavesinanaluminiumplate.q2001ElsevierScienceLtd.Allr

5、ightsreserved.Keywords:Dispersion;Guidedwaves;Lambwaves;Long-rangetesting1.Background[6,7]andcomposites[8],pipeline[9±11]andplate[12]inspection.Inlong-rangeapplications,theaimistoinspect1.1.Guidedwavesandnon-destructiveinspectionlargeareasofastructurerapidly.Muchworkhasbeenpub

6、lishedontheuseofLambwaves1.2.Long-rangeinspectionusingguidedwavesandotherguidedwavesforinspectionpurposesandacomprehensivereviewofapplicationsmaybefoundinInlong-rangeguidedwavetestingapplications,theRef.[1].Verybroadlyspeaking,theuseofguidedwavesguidedwavesareexcitedbyashortbu

7、rstofenergy(thefornon-destructiveinspectionpurposesfallsintotwocat-inputsignal)appliedbyasuitabletransduceratonelocationegoriesdependingonthedistanceofpropagation.Firstly,onastructure.Theexcitationcausesapacketofguidedthereareshort-rangeapplications,whereguidedwavesarewaves(th

8、ewave-packet)topropagateawayfromthetrans-usedtoobtaininformat